By "working for you", do you mean that you don't have a
> red face? Yes, that's fine, but if you read my initial
> email, I said "there's still (opaque) white drawn in the
> background" for this case. What do you get? I predict
> that you do.
Oh, I did misread. Yes, I was getting rid of the red but didn't
notice the white background of the canvas.
This does, as you noted, show up whether or not you set alpha to zero
and whether or not you draw the figure frame. The reason is, when I
initialize the agg buffer (src/_backend_agg.cpp) I do
rendererBase->clear(agg::rgba(1, 1, 1));
which sets a default background of white with a default alpha of 1. I
just tested the following change to line 46:
rendererBase->clear(agg::rgba(1, 1, 1, 0));
Ie, manually set the alpha of the background color to zero, and it
worked as expected with your example. Now the background is truly
transparent. I also checked this in CVS but you can just change the
one line to get the same result.